No abstract

Zinc oxide (ZnO) has received lot of attention as a nanostructured material because of unique properties rendering it for various applications. Severe drilling problems like pipe sticking, formation damage and high torque and drag are common in extended reach hydrocarbon wells that limit the performance of drilling operations. Bentonite (MMT) is commonly used as a rheology modifier, and attapulgite (ATP) has good Fann viscosity for use in drilling fluids, but both clays face the limitations of flocculation and instability at high temperature and pressure conditions (HTHP). ZnO–clay nanocomposites were formed by incorporating nano‐ZnO in nano‐modified MMT and ATP to maintain remarkable colloidal dispersion and superior rheology, thus enabling homogeneous drilling fluid recipes. ZnO–clay nanocomposites were characterized using scanning electron microscopy and X‐ray diffraction. After successive laboratory investigations, drilling fluid compositions of certain proportions of water and MMT in the presence of ZnO–clay nanocomposite yielded perfect stability at high temperatures and pressure, i.e. stable drilling fluid rheology at HTHP conditions. The best‐recorded results are reported in this paper, and the properties focused here are the plastic viscosity and yield point. Copyright © 2014 John Wiley & Sons, Ltd.

No abstract

Above a certain critical speed, sliding systems with frictional heating such as brakes and clutches can exhibit thermoelastic instability in which non-uniform perturbations develop in the pressure and temperature ÿelds. A method is described in which the transient thermomechanical behaviour of such systems is approximated by a reduced order model, describing one or more dominant perturbations or eigenfunctions. The goal is to construct a mathematical model of the system with a modest number of degrees of freedom.If a single dominant perturbation is used, an integral expression can be written for the evolution of the perturbation with time. A more accurate description involving several terms requires that the transient behaviour be generated by a sequence of operations in which the sliding speed is piecewise constant. Both models are evaluated by comparison with a direct numerical simulation and prove to give good accuracy with a dramatic reduction in computing time. ?

No abstract